Abstract: Objective To evaluate the expression of hypoxia-related carbonic anhydrase-9（CA-9） in colorectal carcinoma and its possible relation with clinical and pathologic indications of colorectal carcinoma.Methods Expression of CA-9 in 43 cases of colorectal carcinoma was detected with immunohistochemical method and its relation with pathological grade,clinical stage,and metastasis of colorectal carcinoma was evaluated.Results The positive and negative CA-9 expression was in 25 and 18 cases of colorectal carcinoma,respectively.The CA-9 expression was closely related with the invasion depth（P=0.005）,lymph node metastasis（P=0.040）,histological grade（P=0.047）,and clinical stage（P=0.002） of colorectal carcinoma.Conclusion The positive expression rate of CA-9 is high in metastatic colorectal carcinoma,indicating that CA-9 may be an effective prognostic factor for colorectal carcinoma.